Bad Transmisson or something else.

[microAmp]

1999
GMC
Sierra 1500 - "new body style not classic"
4.8L V8 Automatic
SL
No modifications to engine or transmission, just bigger tires.
94,000 miles.

Started having issues about 5 days ago. When doing light acceleration, 1 MPH increase per second at 45-50 MPH, and going from 3rd to 4th (Overdrive?) It wouldn't make up it's mind to be in 3rd or 4th, causing a slight shudder, vibration and wouldn't increase in speed either, staying stuck at 50. But if I gave it more gas, the RPMs would kick up more getting speed in 3rd and then change to 4th with no issues. This has happened several times since the start of 5 days ago.

Also, while just recently going and coming back from the dealer to test drive two Ford Escapes. The transmission at 70 MPH didn't want to go from 3rd to 4th. RPMs were at about 3500, maybe 3000'ish. It eventually went to 4th but playing around with the acceleration, giving it no gas and the RPMs drop to a little below 2000 and some gas to RPMs to 3000'ish. This is just recently, today.

Just wondering if the transmission is going bad or would a filter + flush fix my issue. I had 2 transmission oil flushes, for sure, 1st one may have filter changed (doubtful to be honest) but can't find paper work on the 1st one. 2nd one was just a flush, silly me thought they did filter also. *doh*

<--- Really doesn't want to buy a new vehicle.

 

[Zenmervolt]

Sounds like the 3rd-4th shift solenoid is failing, but it's impossible to say for sure without opening up the transmission. Unfortunately, the cost of opening up the transmission to check it isn't that much different from replacing the part so you'll be pretty much committed to either replacing the part or having it rebuilt.

I doubt that a flush and new filter would solve the issue that you describe.

The good news is that the transmissions in those trucks are incredibly common and therefore relatively inexpensive to repair/rebuild.

ZV

 

[microAmp]

Thanks for the information Zenmervolt, only reason I asked about the flush/filter was that I mentioned to a co-worker Tuesday. He said he had similar issues like that and had the filter changed out and voila, no issue.

Any idea how much would that cost? Ball park range?

 

[Vette73]

I would not flush. Just open the pan and change the filter and that fluid to see what happens.

But yea sounds like a solenoid is acting up.

 

[Zenmervolt]

Originally posted by: microAmp
Thanks for the information Zenmervolt, only reason I asked about the flush/filter was that I mentioned to a co-worker Tuesday. He said he had similar issues like that and had the filter changed out and voila, no issue.

Any idea how much would that cost? Ball park range?

Depending on how common the transmission is, a rebuild will probably be in the $1,000-$2,000 range, I don't know the specifics for Chevy units, but late-model Ford transmissions tend to be in that range and it's a decent rough estimate.

I would recommend a full rebuild over just replacing the solenoid if a simple refill of the fluid doesn't help. The full rebuild won't cost that much more (most of the labor is in dropping and opening the transmission) and it will give you the confidence that the transmission will last for a long time into the future.

I will also add that GM transmissions, especially in trucks, are usually very robust units, having one start to fail at only 94,000 miles is uncommon.

ZV

 

[microAmp]

OK, thanks for the information, I may just opt for new vehicle then. Transmission makes a 3rd issue in two months, rack and pinion leaking and water pump leaking last time. Would hate to see what else falls apart in the short term future. Even though nothing else might not go wrong, sort of becoming a money sink. Hmm.. will have to mull over it.

 

[Zenmervolt]

Originally posted by: microAmp
OK, thanks for the information, I may just opt for new vehicle then. Transmission makes a 3rd issue in two months, rack and pinion leaking and water pump leaking last time. Would hate to see what else falls apart in the short term future. Even though nothing else might not go wrong, sort of becoming a money sink. Hmm.. will have to mull over it.

Water pump is normal at around 100,000 miles. Rack and pinion isn't all that common, but it's not unheard of. And, as I said, the transmission issue is unusual.

In general, if the body is straight and everything else is good, it's less expensive to fix the vehicle you have than it is to buy a new vehicle. On the other hand, there is something to be said for the piece of mind that you mention. Good luck with your decision.

ZV